The present invention relates to chain link assemblies and more particularly to an improved bushing structure for use in a chain link assembly which permits the combination of a bushing and roller into one element and which provides full joint bearing areas throughout the angle of flexure required for the engagement of the chain link assembly with a driving sprocket.
At present, chain link assemblies are made by welding, casting or otherwise fixedly securing one-piece bushings or barrels to the sidebars which form the closed end of the chain link assembly. The number of links, as required or desired, are joined together in tandem fashion to form the chain assembly by inserting a pin through the barrel at its closed end of the first link to complete the chain link assembly.
Bushed chain link assemblies are at present completed and made by fixedly securing one-piece bushings to the first ends of sidebars containing a double-D pitched openings therein. The present used milled barrels include an inside diameter bore which will matingly and snugly receive the outside diameter of a pin inserted therethrough. In such constructions, the milled end dimension of the ends of the bushings are greater than the inside diameter of the bushing, a structure which permits material to enter into the space between the outside diameter of the pin and the inside diameter of the barrel, thus resulting in increased wear when the chain assemblies are employed handling heavy loads under severe operating conditions. The rapid wear of such links and the attendant costs in replacing the worn chain links is undesirable.
In welded chain link assemblies, the working inside width of the chain, which is defined as the width of the barrel or backing between the sidebars, is reduced by the thickness of the weld which secures the ends of the barrel to the inside surface of the sidebars. Thus, such welded chain assemblies are either wider than required or the inside width of the sprocket contact is less, such that there is not full bushing link contact during chain link articulation about the drive sprocket. Additionally, in such welded steel chain assemblies, there are pockets formed between the outside barrel surface and the sidebar pitch hole. These pockets tend to receive and to pack the conveyed material which can jam and freeze the chain joint thereby preventing articulation around the drive sprockets. Furthermore, in such welded steel chain link assemblies the material selection for the barrel or bushing and the material selected for the sidebar is limited to the same or a similar material because of the welding requirements of the material. Also, the problem of weld joint susceptibility to embrittlement, grain size growth, corrosion and fatigue are problems encountered with the use of welded chain link assemblies. Finally, welded constructions lack inherent positive alignment of the sidebars relative to each other because they are fixed by welding. Accordingly, such welded chain links cannot be disassembled and prevents the replacement of worn barrels with new barrels.
Chain link assemblies made by casting have been suggested and are used in industry, but such cast designs require that the same or single material be used for casting the entire link, comprised of sidebars and the barrel or bushing. Accordingly, such cast designs are therefore limited to specific castable materials, which materials do not provide the desired increased wear area of the overall barrel width and do not provide the desired angle of articulation about the drive sprocket. Moreover, such cast assemblies prevent the replacement of worn links and the rebuilding of chain assemblies as wear recurs.
U.S. Pat. No. 4,129,045 to K. Kishitani shows a replaceable cover surrounding each bushing for protecting the external surface of the bushing from wear. However, such an assembly fails to provide for the necessary clearance between the pin and the inside diameter of the bushing and requires a complex retaining means for anchoring each of the covers in place about each of the bushings.